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Knowing What Students Know: The Science and Design of Eduacational Assessment
For example, it is now common wisdom that a task used to observe mathematical reasoning should include words and expressions in general use and not those associated with particular cultures or regions; the latter might result in a lack of comparable score meanings across groups of examinees.
Currently, bias tends to be identified through expert review of items. Such a finding is merely judgmental, however, and in and of itself may not warrant removal of items from an assessment. Also used are statistical differential item functioning (DIF) analyses, which identify items that produce differing results for members of particular groups after the groups have been matched in ability with regard to the attribute being measured (Holland and Thayer, 1988). However, DIF is a statistical finding and again may not warrant removal of items from an assessment. Some researchers have therefore begun to supplement existing bias-detection methods with cognitive analyses designed to uncover the reasons why items are functioning differently across groups in terms of how students think about and approach the problems (e.g., Lane, Wang, and Magone, 1996; Zwick and Ercikan, 1989).
A particular set of fairness issues involves the testing of students with disabilities. A substantial number of children who participate in assessments do so with accommodations intended to permit them to participate meaningfully. For instance, a student with a severe reading and writing disability might be able to take a chemistry test with the assistance of a computer-based reader and dictation system. Unfortunately, little evidence currently exists about the effects of various accommodations on the inferences one might wish to draw about the performance of individuals with disabilities (NRC, 1997), though some researchers have taken initial steps in studying these issues (Abedi, Hofstetter, and Baker, 2001). Therefore, cognitive analyses are also needed to gain insight into how accommodations affect task demands, as well as the validity of inferences drawn from test scores obtained under such circumstances.
In some situations, rather than aiming to design items that are culture-or background-free, a better option may be to take into account learner history in the interpretation of responses to the assessment. The distinction between conditional and unconditional inferences deserves attention because it may provide a key to resolving some of the thorniest issues in assessment today, including equity and student choice of tasks.
Conditional Versus Unconditional Inferences
To some extent in any assessment, given students of similar ability, what is relatively difficult for some students may be relatively easy for others, depending on the degree to which the tasks relate to the knowledge structures students have, each in their own way, constructed (Mislevy, 1996). From the traditional perspective, this is “noise,” or measurement error, and if